Travis: compile the interfaces only with clang
Travis: compile the interfaces only with clang

Saurabh7/shogun,geektoni/shogun,besser82/shogun,lisitsyn/shogun,besser82/shogun,lambday/shogun,lambday/shogun,Saurabh7/shogun,karlnapf/shogun,shogun-toolbox/shogun,karlnapf/shogun,shogun-toolbox/shogun,lambday/shogun,shogun-toolbox/shogun,karlnapf/shogun,sorig/shogun,lisitsyn/shogun,lisitsyn/shogun,Saurabh7/shogun,besser82/shogun,sorig/shogun,shogun-toolbox/shogun,geektoni/shogun,karlnapf/shogun,besser82/shogun,shogun-toolbox/shogun,geektoni/shogun,karlnapf/shogun,sorig/shogun,karlnapf/shogun,sorig/shogun,shogun-toolbox/shogun,Saurabh7/shogun,lambday/shogun,Saurabh7/shogun,besser82/shogun,Saurabh7/shogun,lisitsyn/shogun,lisitsyn/shogun,lambday/shogun,geektoni/shogun,Saurabh7/shogun,lambday/shogun,sorig/shogun,Saurabh7/shogun,geektoni/shogun,Saurabh7/shogun,sorig/shogun,geektoni/shogun,besser82/shogun,lisitsyn/shogun